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-rw-r--r--kernel/rcu/tree.h1
-rw-r--r--kernel/rcu/tree_plugin.h140
2 files changed, 77 insertions, 64 deletions
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index 71821d59d95c..b280a843bd2c 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -257,7 +257,6 @@ struct rcu_data {
};
/* Values for nocb_defer_wakeup field in struct rcu_data. */
-#define RCU_NOCB_WAKE_OFF -1
#define RCU_NOCB_WAKE_NOT 0
#define RCU_NOCB_WAKE 1
#define RCU_NOCB_WAKE_FORCE 2
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index ad0156b86937..5a2aa9c4e569 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -33,10 +33,6 @@ static inline bool rcu_current_is_nocb_kthread(struct rcu_data *rdp)
return false;
}
-static inline bool rcu_running_nocb_timer(struct rcu_data *rdp)
-{
- return (timer_curr_running(&rdp->nocb_timer) && !in_irq());
-}
#else
static inline int rcu_lockdep_is_held_nocb(struct rcu_data *rdp)
{
@@ -48,11 +44,6 @@ static inline bool rcu_current_is_nocb_kthread(struct rcu_data *rdp)
return false;
}
-static inline bool rcu_running_nocb_timer(struct rcu_data *rdp)
-{
- return false;
-}
-
#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
static bool rcu_rdp_is_offloaded(struct rcu_data *rdp)
@@ -72,8 +63,7 @@ static bool rcu_rdp_is_offloaded(struct rcu_data *rdp)
rcu_lockdep_is_held_nocb(rdp) ||
(rdp == this_cpu_ptr(&rcu_data) &&
!(IS_ENABLED(CONFIG_PREEMPT_COUNT) && preemptible())) ||
- rcu_current_is_nocb_kthread(rdp) ||
- rcu_running_nocb_timer(rdp)),
+ rcu_current_is_nocb_kthread(rdp)),
"Unsafe read of RCU_NOCB offloaded state"
);
@@ -1692,56 +1682,69 @@ bool rcu_is_nocb_cpu(int cpu)
return false;
}
-/*
- * Kick the GP kthread for this NOCB group. Caller holds ->nocb_lock
- * and this function releases it.
- */
-static bool wake_nocb_gp(struct rcu_data *rdp, bool force,
- unsigned long flags)
- __releases(rdp->nocb_lock)
+static bool __wake_nocb_gp(struct rcu_data *rdp_gp,
+ struct rcu_data *rdp,
+ bool force, unsigned long flags)
+ __releases(rdp_gp->nocb_gp_lock)
{
bool needwake = false;
- struct rcu_data *rdp_gp = rdp->nocb_gp_rdp;
- lockdep_assert_held(&rdp->nocb_lock);
if (!READ_ONCE(rdp_gp->nocb_gp_kthread)) {
- rcu_nocb_unlock_irqrestore(rdp, flags);
+ raw_spin_unlock_irqrestore(&rdp_gp->nocb_gp_lock, flags);
trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
TPS("AlreadyAwake"));
return false;
}
- if (READ_ONCE(rdp->nocb_defer_wakeup) > RCU_NOCB_WAKE_NOT) {
- WRITE_ONCE(rdp->nocb_defer_wakeup, RCU_NOCB_WAKE_NOT);
- del_timer(&rdp->nocb_timer);
+ if (rdp_gp->nocb_defer_wakeup > RCU_NOCB_WAKE_NOT) {
+ WRITE_ONCE(rdp_gp->nocb_defer_wakeup, RCU_NOCB_WAKE_NOT);
+ del_timer(&rdp_gp->nocb_timer);
}
- rcu_nocb_unlock_irqrestore(rdp, flags);
- raw_spin_lock_irqsave(&rdp_gp->nocb_gp_lock, flags);
+
if (force || READ_ONCE(rdp_gp->nocb_gp_sleep)) {
WRITE_ONCE(rdp_gp->nocb_gp_sleep, false);
needwake = true;
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("DoWake"));
}
raw_spin_unlock_irqrestore(&rdp_gp->nocb_gp_lock, flags);
- if (needwake)
+ if (needwake) {
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("DoWake"));
wake_up_process(rdp_gp->nocb_gp_kthread);
+ }
return needwake;
}
/*
+ * Kick the GP kthread for this NOCB group.
+ */
+static bool wake_nocb_gp(struct rcu_data *rdp, bool force)
+{
+ unsigned long flags;
+ struct rcu_data *rdp_gp = rdp->nocb_gp_rdp;
+
+ raw_spin_lock_irqsave(&rdp_gp->nocb_gp_lock, flags);
+ return __wake_nocb_gp(rdp_gp, rdp, force, flags);
+}
+
+/*
* Arrange to wake the GP kthread for this NOCB group at some future
* time when it is safe to do so.
*/
static void wake_nocb_gp_defer(struct rcu_data *rdp, int waketype,
const char *reason)
{
- if (rdp->nocb_defer_wakeup == RCU_NOCB_WAKE_OFF)
- return;
- if (rdp->nocb_defer_wakeup == RCU_NOCB_WAKE_NOT)
- mod_timer(&rdp->nocb_timer, jiffies + 1);
- if (rdp->nocb_defer_wakeup < waketype)
- WRITE_ONCE(rdp->nocb_defer_wakeup, waketype);
+ unsigned long flags;
+ struct rcu_data *rdp_gp = rdp->nocb_gp_rdp;
+
+ raw_spin_lock_irqsave(&rdp_gp->nocb_gp_lock, flags);
+
+ if (rdp_gp->nocb_defer_wakeup == RCU_NOCB_WAKE_NOT)
+ mod_timer(&rdp_gp->nocb_timer, jiffies + 1);
+ if (rdp_gp->nocb_defer_wakeup < waketype)
+ WRITE_ONCE(rdp_gp->nocb_defer_wakeup, waketype);
+
+ raw_spin_unlock_irqrestore(&rdp_gp->nocb_gp_lock, flags);
+
trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, reason);
}
@@ -1968,13 +1971,14 @@ static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_alldone,
rdp->qlen_last_fqs_check = len;
if (!irqs_disabled_flags(flags)) {
/* ... if queue was empty ... */
- wake_nocb_gp(rdp, false, flags);
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+ wake_nocb_gp(rdp, false);
trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
TPS("WakeEmpty"));
} else {
+ rcu_nocb_unlock_irqrestore(rdp, flags);
wake_nocb_gp_defer(rdp, RCU_NOCB_WAKE,
TPS("WakeEmptyIsDeferred"));
- rcu_nocb_unlock_irqrestore(rdp, flags);
}
} else if (len > rdp->qlen_last_fqs_check + qhimark) {
/* ... or if many callbacks queued. */
@@ -1989,10 +1993,14 @@ static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_alldone,
smp_mb(); /* Enqueue before timer_pending(). */
if ((rdp->nocb_cb_sleep ||
!rcu_segcblist_ready_cbs(&rdp->cblist)) &&
- !timer_pending(&rdp->nocb_bypass_timer))
+ !timer_pending(&rdp->nocb_bypass_timer)) {
+ rcu_nocb_unlock_irqrestore(rdp, flags);
wake_nocb_gp_defer(rdp, RCU_NOCB_WAKE_FORCE,
TPS("WakeOvfIsDeferred"));
- rcu_nocb_unlock_irqrestore(rdp, flags);
+ } else {
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("WakeNot"));
+ }
} else {
rcu_nocb_unlock_irqrestore(rdp, flags);
trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("WakeNot"));
@@ -2118,11 +2126,7 @@ static void nocb_gp_wait(struct rcu_data *my_rdp)
bypass = true;
}
rnp = rdp->mynode;
- if (bypass) { // Avoid race with first bypass CB.
- WRITE_ONCE(my_rdp->nocb_defer_wakeup,
- RCU_NOCB_WAKE_NOT);
- del_timer(&my_rdp->nocb_timer);
- }
+
// Advance callbacks if helpful and low contention.
needwake_gp = false;
if (!rcu_segcblist_restempty(&rdp->cblist,
@@ -2168,11 +2172,18 @@ static void nocb_gp_wait(struct rcu_data *my_rdp)
my_rdp->nocb_gp_bypass = bypass;
my_rdp->nocb_gp_gp = needwait_gp;
my_rdp->nocb_gp_seq = needwait_gp ? wait_gp_seq : 0;
- if (bypass && !rcu_nocb_poll) {
- // At least one child with non-empty ->nocb_bypass, so set
- // timer in order to avoid stranding its callbacks.
+ if (bypass) {
raw_spin_lock_irqsave(&my_rdp->nocb_gp_lock, flags);
- mod_timer(&my_rdp->nocb_bypass_timer, j + 2);
+ // Avoid race with first bypass CB.
+ if (my_rdp->nocb_defer_wakeup > RCU_NOCB_WAKE_NOT) {
+ WRITE_ONCE(my_rdp->nocb_defer_wakeup, RCU_NOCB_WAKE_NOT);
+ del_timer(&my_rdp->nocb_timer);
+ }
+ if (!rcu_nocb_poll) {
+ // At least one child with non-empty ->nocb_bypass, so set
+ // timer in order to avoid stranding its callbacks.
+ mod_timer(&my_rdp->nocb_bypass_timer, j + 2);
+ }
raw_spin_unlock_irqrestore(&my_rdp->nocb_gp_lock, flags);
}
if (rcu_nocb_poll) {
@@ -2344,15 +2355,18 @@ static bool do_nocb_deferred_wakeup_common(struct rcu_data *rdp)
{
unsigned long flags;
int ndw;
+ struct rcu_data *rdp_gp = rdp->nocb_gp_rdp;
int ret;
- rcu_nocb_lock_irqsave(rdp, flags);
- if (!rcu_nocb_need_deferred_wakeup(rdp)) {
- rcu_nocb_unlock_irqrestore(rdp, flags);
+ raw_spin_lock_irqsave(&rdp_gp->nocb_gp_lock, flags);
+
+ if (!rcu_nocb_need_deferred_wakeup(rdp_gp)) {
+ raw_spin_unlock_irqrestore(&rdp_gp->nocb_gp_lock, flags);
return false;
}
- ndw = READ_ONCE(rdp->nocb_defer_wakeup);
- ret = wake_nocb_gp(rdp, ndw == RCU_NOCB_WAKE_FORCE, flags);
+
+ ndw = rdp_gp->nocb_defer_wakeup;
+ ret = __wake_nocb_gp(rdp_gp, rdp, ndw == RCU_NOCB_WAKE_FORCE, flags);
trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("DeferredWake"));
return ret;
@@ -2373,7 +2387,10 @@ static void do_nocb_deferred_wakeup_timer(struct timer_list *t)
*/
static bool do_nocb_deferred_wakeup(struct rcu_data *rdp)
{
- if (rcu_nocb_need_deferred_wakeup(rdp))
+ if (!rdp->nocb_gp_rdp)
+ return false;
+
+ if (rcu_nocb_need_deferred_wakeup(rdp->nocb_gp_rdp))
return do_nocb_deferred_wakeup_common(rdp);
return false;
}
@@ -2443,17 +2460,15 @@ static long rcu_nocb_rdp_deoffload(void *arg)
swait_event_exclusive(rdp->nocb_state_wq,
!rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB |
SEGCBLIST_KTHREAD_GP));
- rcu_nocb_lock_irqsave(rdp, flags);
- /* Make sure nocb timer won't stay around */
- WRITE_ONCE(rdp->nocb_defer_wakeup, RCU_NOCB_WAKE_OFF);
- rcu_nocb_unlock_irqrestore(rdp, flags);
- del_timer_sync(&rdp->nocb_timer);
-
/*
- * Theoretically we could set SEGCBLIST_SOFTIRQ_ONLY with CB unlocked
- * and IRQs disabled but let's be paranoid.
+ * Lock one last time to acquire latest callback updates from kthreads
+ * so we can later handle callbacks locally without locking.
*/
rcu_nocb_lock_irqsave(rdp, flags);
+ /*
+ * Theoretically we could set SEGCBLIST_SOFTIRQ_ONLY after the nocb
+ * lock is released but how about being paranoid for once?
+ */
rcu_segcblist_set_flags(cblist, SEGCBLIST_SOFTIRQ_ONLY);
/*
* With SEGCBLIST_SOFTIRQ_ONLY, we can't use
@@ -2517,8 +2532,7 @@ static long rcu_nocb_rdp_offload(void *arg)
* SEGCBLIST_SOFTIRQ_ONLY mode.
*/
raw_spin_lock_irqsave(&rdp->nocb_lock, flags);
- /* Re-enable nocb timer */
- WRITE_ONCE(rdp->nocb_defer_wakeup, RCU_NOCB_WAKE_NOT);
+
/*
* We didn't take the nocb lock while working on the
* rdp->cblist in SEGCBLIST_SOFTIRQ_ONLY mode.
generated by cgit v1.2.3 (git 2.25.1) at 2024-06-18 11:22:10 +0000